The features and capabilities of cellular telephones and other handheld devices continue to improve. Until recently, cellular telephones were merely able to initiate and receive voice calls. Today, cellular telephones incorporate many different functions, such as sending and receiving Multimedia Messaging Service (MMS) or Short Message Service (SMS) transmissions (“text messages”) to other cellular subscribers, playing music and video files, sending and receiving e-mail messages, taking pictures, recording video and audio, internet browsing, and incorporating the Personal Information Management (PIM) functions typically associated with a Personal Digital Assistant (PDA). Some cellular telephones also incorporate a removable media slot to store and access data on a removable media card using a communication interface such as a Multimedia Card (MMC) interface, a Secure Digital (SD) interface, a Universal Serial Bus (USB), or a Serial Advanced Technology Attachment (SATA) interface.
Mobile Network Operators (MNOs) that sell or provide these enhanced cellular telephones to their subscribers are faced with a variety of challenges. For example, an MNO may want to charge a monthly fee in order to use certain features of a telephone, such as a built-in camera. In this case, the MNO may charge a subscriber a fee in order to take pictures with the cellular telephone using a camera application (software or firmware) provided by the MNO that operates the camera. The MNO may want to enable or disable an application depending on whether a subscriber has paid for that service or feature. In doing so, the MNO may increase the monthly revenue received from an individual subscriber.
In another example, an MNO may want to allow third party software developers to write useful applications for the cellular telephone hardware used by the MNO's subscribers. If the cellular telephone hardware is “open platform” (or “open” to selected MNO vendors), third-party software developers may create applications that an MNO may not have the time or resources to develop on its own. If these applications increase the usefulness of the MNO's cellular telephone hardware, more users may subscribe to that MNO's network. However, the MNO may want to have ultimate control over whether a certain application is allowed to execute on its cellular telephone hardware, or access certain features of the hardware. Such control is desirable in the event that a software application contains a software virus that could damage the cellular telephone software or hardware or render it inoperable. This control is also desirable if a third-party application circumvents subscription features offered by the MNO, such as a software application that operates the cellular telephone camera hardware without requiring a subscription fee payable to the MNO.